I am getting into Masters ski racing, especially GS. Which brands have the best reputation when it comes to racing skis? What do you use?

Fischer,K2,Atomic, Dynastar, Head, Rossignol, Dynamic, Stockli. Not necessarily in that order. It is the racer and how the skiis are prepared, not the ski itself. A bad tune will loose the race, A good tune and a good racer may win it.
l have not raced in many years, the legs are shot.

Dymastar Atomic Rossignol Fisher

It seems like most high school racers ski on Atomics.

l like Atomic (hence the screen name)- their skis have a great race chassis, proven in World Cup competition and generally great reviews. At some races l go to you will see 30-40% of the racers on Atomics. l see lots of high school racers on Fischers.